[Renal SGLT2 inhibitors, new agents for the management of type 2 diabetes]

Kidney plays a role in glucose homeostasis, not only by its capacity to produce glucose through local gluconeogenesis, but also, and even more important in presence of diabetes, by its capacity to excrete glucose in urine when hyperglycaemia exceeds tubular reabsorption threshold. Such reabsorption depends on sodium-glucose cotransporters-2 (SGLT2), which can be blocked by selective inhibitors. These pharmacological agents augment glucosuria and reduce hyperglycaemia independently of insulin. Some have already proven their efficacy to improve glucose control, in monotherapy or in combination, while promoting weight loss and without inducing hypoglycaemia. Dapagliflozin should be the first medication of this new pharmacological class to be commercialized for the management of type 2 diabetes.

[Strategies avoiding inertia and non compliance in clinical trials]

Randomised controlled trials play a key role in evidence-based medicine as far as the assessment of both efficacy and safety of drugs is concerned. Various strategies are used to avoid physician's inertia and to combat patient's non compliance, two pitfalls that may hinder the demonstration of the therapeutic efficacy of the drug. Clinical inertia may be limited by titration, forced or optional, driven by therapeutic targets, or by the use, if necessary, of rescue medications. Compliance may be verified by "pill count". This simple technique allows to exclude non compliant patients when they are detected during the placebo run-in period before randomisation or not to take into account patients with poor compliance in the final evaluation by using a statistical analysis restricted to individuals who have strictly adhered to the study protocol ("per protocol analysis"). Self-monitoring and patient's empowerment in the treatment also contribute to improve drug compliance. Clinicians may take advantage of these approaches derived from clinical trials to improve their daily practice.

[Optimisation of pharmacological therapy in a patient with a newly diagnosed type 2 diabetes]

The diabetic patient, when type 2 diabetes is newly diagnosed, raises a therapeutic problem commonly observed in clinical practice, which is more complex than expected at first glance. The physician has to select the most appropriate antidiabetic oral agent as first choice, to consider the potential of using combined glucose-lowering therapies, to fix glycaemic target taking into account the individual benefit/risk ratio, and to offer the best protection against cardiovascular complications. The present clinical case illustrates such therapeutic problem describing a patient with a high cardiovascular risk profile who experienced a hypoglycaemic episode after the prescription of glibenclamide following the discovery of a moderate hyperglycaemia.

[Brain, a gluco-dependent organ: toxic effects of hypoglycaemia and hyperglycaemia]

Glucose is almost the only energy substrate for the brain. Such glucose dependence explains why any large variation of plasma glucose levels could lead to cerebral dysfunction, which may be severe and progress to a coma. Hypoglycaemic coma, the most common one, has a pure metabolic origin (neuroglucopenia) whereas hyperglycaemic coma is more complex and mainly due to osmotic disturbances. Besides acute changes of plasma glucose concentrations, it is generally recognized that more subtle chronic or recurrent glucose abnormalities could also result in brain dysfunction. However, such clinical consequences are more difficult to assess in clinical practice. Nevertheless, learning perturbations in young patients with type 1 diabetes and memory losses, sometimes severe and subject to progress to dementia ("diabetic encephalopathy") in older type 1 or type 2 diabetic patients, have been reported, although with some controversy. The present paper summarizes the current knowledge of both acute and chronic cerebral dysfunctions following perturbations of blood glucose levels in diabetic patients.

[Alcohol, insulin sensitivity and diabetes]

The relationship between alcohol consumption and insulin resistance shows a U-shaped curve: insulin resistance is minimal in individuals with regular mild to moderate alcohol consumption and increases in both heavy drinkers and subjects without any alcohol consumption. These favourable metabolic effects on insulin sensitivity of moderate alcohol consumption may explain the significant reduction in the development of type 2 diabetes and the risk of cardiovascular complications reported in numerous epidemiological studies. This latter effect has also reported in patients with diabetes mellitus, although this observation remains controversial. However, alcohol consumption could increase the global risk of hypoglycaemia, both in the fasting state and after a meal (reactive hypoglycaemia) in both diabetic and nondiabetic subjects. These latter effects may result from a direct inhibition of gluconeogenesis, from a reduced secretion of counterregulatory hormones and/or from an alcohol-induced inappropriate behaviour.

[Muscular exercise in the diabetic patient]

Muscular exercise is recommended in patients with type 1 or type 2 diabetes mellitus and is part of the overall management, in combination with diet, oral antidiabetic agents and/or insulin. From a pathophysiological point of view, regular physical activity enhances insulin sensitivity, thus contributing to improve blood glucose control and to reduce cardiovascular risk factors associated to diabetes mellitus. From a practical point of view, however, muscular exercise in a diabetic patient requires special caution, in particular careful selection of the type of exercise, respect of metabolic and/or cardiovascular contraindications, and appropriate adjustment of current pharmacological/dietary treatment.

[Hormonal-metabolic adaptations to muscular exercise]

Physical exercise induces numerous metabolic and hormonal changes that may be influenced by various factors, among which the intensity and the duration of the exertion seem to play a major role besides the possible influence of the intake of exogenous substrates. Such modifications are necessary to satisfy the marked increase in energy demand by exercising muscles, while maintaining plasma glucose concentrations within physiological range. The purpose of the present concise review is to analyse the most important fuel-hormonal adaptations observed during short heavy muscular exercise or during prolonged exercise of moderate intensity as well as those observed after physical training in normal subjects.

Fructose utilization during exercise in men: rapid conversion of ingested fructose to circulating glucose

The aim of the present study was to compare the metabolic fate of repeated doses of fructose or glucose ingested every 30 min during long-duration moderate-intensity exercise in men. Healthy volunteers exercised for 3 h on a treadmill at 45% of their maximal oxygen consumption rate. "Naturally labeled" [13C]glucose or [13C]fructose was given orally at 25-g doses every 30 min (total feeding: 150 g; n = 6 in each group). Substrate utilization was evaluated by indirect calorimetry, and exogenous sugar oxidation was measured by isotope ratio mass spectrometry on expired CO2. Results were corrected for baseline drift in 13C/12C ratio in expired air due to exercise alone. Fructose conversion to plasma glucose was measured combining gas chromatography and isotope ratio mass spectrometry. Most of the ingested glucose was oxidized: 81 +/- 4 vs. 57 +/- 2 g/3 h for fructose (2P < 0.005). Exogenous glucose covered 20.8 +/- 1.4% of the total energy need (+/- 6.7 MJ) compared with 14.0 +/- 0.6% for fructose (2P < 0.005). The contribution of total carbohydrates was significantly higher and that of lipids significantly lower with glucose than with fructose. The blood glucose response was similar in both protocols. From 90 to 180 min, 55-60% of circulating glucose was derived from ingested fructose. In conclusion, when ingested repeatedly during moderate-intensity prolonged exercise, fructose is metabolically less available than glucose, despite a high rate of conversion to circulating glucose.

Effects of a 1-year treatment with a low-dose combined oral contraceptive containing ethinyl estradiol and cyproterone acetate on glucose and insulin metabolism

OBJECTIVE

To study the effects of the slightly estrogen-dominant monophasic low-dose oral contraceptive (OC) Diane-35 (Schering AG, Berlin, Germany) (35 micrograms ethinyl estradiol [EE2] + 2 mg cyproterone acetate, a 17 alpha-hydroxyprogesterone derivative [17-OHP]) on glucose and insulin metabolism.

DESIGN

Seven healthy young women were investigated by using the euglycemic hyperinsulinemic glucose clamp technique (insulin delivery rate = 100 mU/kg per hour for 120 minutes). This test was performed, after an overnight fast, during the last 7 days of a spontaneous cycle and within the last 5 days of pill intake during the sixth and twelfth cycle of a continuous treatment with Diane-35 in each subject.

RESULTS

The three indexes measuring the insulin-induced glucose disposal during the clamp (glucose infusion rate, glucose metabolic clearance rate, and glucose infusion rate divided by plasma insulin plateau levels) were not significantly affected by Diane-35. In contrast, the metabolic clearance rate of the exogenous insulin infused during the clamp tended to be slightly increased with Diane-35 (significant after 6 but not after 12 cycles).

CONCLUSION

These results suggest that a 1-year treatment with the OC Diane-35, which contains EE2 + a 17-OHP rather than a 19-nortestosterone derivative as the progestogen compound, does not significantly alter peripheral (presumably muscular) insulin sensitivity but slightly increases insulin (presumably hepatic) clearance.

Effects of ethinyl estradiol combined with desogestrel and cyproterone acetate on glucose tolerance and insulin response to an oral glucose load: a one-year randomized, prospective, comparative trial

To investigate the effects of two slightly estrogen-dominant, monophasic, low-dose oral contraceptives on carbohydrate metabolism, 40 healthy young women were randomly allocated to receive either 30 micrograms of ethinyl estradiol + 150 micrograms of desogestrel, a 19-nortestosterone-derived progestin (Marvelon; n = 21) or 35 micrograms of ethinyl estradiol + 2 mg of cyproterone acetate, a 17-acetoxyprogesterone derivative (Diane-35; n = (19) for a prospective observation period of 1 year. At baseline, 6, and 12 months, blood glucose, plasma insulin, and plasma C-peptide levels were measured during an oral glucose tolerance test. Although the changes were absent (Marvelon) or minimal (Diane-35) at 6 months, both groups had a slight increase in blood glucose levels at 12 months; overall glucose tolerance remaining, however, within the normal range. Plasma insulin levels remained unchanged in the Diane-35-group, which suggested increased insulin resistance, but were significantly decreased in the Marvelon group despite significant rises in plasma C-peptide levels. Comparison of plasma C-peptide and insulin changes suggests enhanced pancreatic insulin secretion and increased hepatic insulin metabolism with both Marvelon and Diane-35.

Effect of osmolality on availability of glucose ingested during prolonged exercise in humans

The aim of this study was to investigate whether the osmolality of a glucose solution, ingested at the beginning of a prolonged exercise bout, affects exogenous glucose disposal. We investigated the hormonal and metabolic response to a 50-g glucose load dissolved in either 200 (protocol A), 400 (protocol B), or 600 (protocol C) ml of water and given orally 15 min after adaptation to exercise in five healthy male volunteers. Naturally labeled [13C]glucose was used to follow the conversion of the ingested glucose to expired-air CO2. Total carbohydrate oxidation (indirect calorimetry) was similar in the three protocols (A, 237 +/- 20; B, 258 +/- 17; C, 276 +/- 20 g/4 h), as was lipid oxidation (A, 128 +/- 4; B, 132 +/- 15; C, 124 +/- 12 g/4 h). Exogenous glucose oxidation rates were similar under the three experimental conditions, and the total amount of exogenous glucose utilized was slightly, but not significantly, increased with the more diluted solution (A, 42.6 +/- 4.4; B, 43.4 +/- 4.1; C, 48.7 +/- 7.2 g/4 h). The blood glucose response was similar in the three protocols. Thus, within the range investigated, the osmolality of the glucose solution ingested had no significant influence either on its oxidation (which was 86-98% of the load ingested) or on the utilization of endogenous carbohydrate, lipid, or protein stores.